Overall health, especially for growing children, really is a sum of the parts. Some days are marked by nonstop activity. Others are marked by a bit more than the recommended amounts of screen time. Some days bedtime comes early. Others are spent staying up late to catch fireflies and watch the stars come out.

Yet, a new study published in the journal The Lancet Child & Adolescent Health found that when three major lifestyle factors—sleep, physical activity and screen time limits—work in unison, kids experience significant cognition benefits.

The problem is, the vast majority of American children don't meet recommendations.

According to the study, which tracked 4,500 American children aged 8 to 11, 95% of the adolescents failed to meet the 24-Hour Movement Guidelines for Children and Youth that were established by the Canadian Society for Exercise Physiology (CSEP). Worse yet, 30% of American kids didn't meet any of the three major recommendations.

Although not widely known here—which is a disadvantage of the study—the 24-Hour Movement Guidelines aren't too ambitious.

It just breaks down recommendations into three categories:

  1. Children aged five to 13 should get nine to 11 hours of uninterrupted sleep each night.
  2. Children should accumulate 60 minutes of physical activity on a daily basis.
  3. Screen time shouldn't exceed two hours daily.

In the United States, it seems families are doing best on meeting the sleep mark, as 51% of the children in the study snoozed for the recommended amount. However, nearly two-in-three children partook in too much screen time and more than 80% of the children studied didn't get enough physical exercise.

When the guidelines were met, the payoffs weren't just for the children's physical health: According to the researchers, children who met all the marks had the most "superior" levels of global cognition, which encompasses measures like memory, attention span, processing speed and language. From there, children who met at least some of the guidelines were better off than the 30% of children who met none at all.

"We know that the behaviors of physical activity, sleep and screen time can independently impact the cognitive health of a child," Jeremy Walsh, lead author of the study and a former post-doctoral fellow at the Children's Hospital of Eastern Ontario, tells CNN. "We really had an opportunity here to look at how meeting each of these guidelines and meeting all of the guidelines relate to cognition in a large sample of American children."

For parents, the takeaway shouldn't (necessarily) be banning screens and sending kids out to play until a strict 7 p.m. bedtime. Rather, one of the most reassuring findings is that the better we aim to be, the better off we are—so even if it feels impractical to hit all three of the guidelines every day, the researchers found that children experience incremental benefits with each guideline they consistently achieve.

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